This invention relates to an acoustooptic modulation element for use in acoustooptically modulating a light beam by an acoustic wave and to an acoustooptic modulation system comprising such an acoustooptic modulation element.
A conventional acoustooptic modulation element of the type described comprises an acoustooptic medium for acoustooptically modulating a single incident light beam by an acoustic wave. More particularly, the acoustooptic medium has a first surface for the incident light beam, a second surface parallel to the first surface, and a third surface between the first and the second surfaces. A transducer is attached to the third surface so as transduce an electric signal into the acoustic wave. When the electric signal has a plurality of frequency components different from one another, the incident light beam which is admitted through the first surface is modulated into a plurality of output light beams by the acoustic wave resulting from the electric signal. The output light beams are emitted through the second surface in directions dependent on the frequency components of the electric signal, as well known in the art. Each of the output light beams is recorded or printed on a recording medium in a known manner.
With the acoustooptic modulation element, the number of the output light beams is determined by the number of the frequency components. This means that each output light beam becomes weaker in intensity with an increase of the frequency components. Accordingly, the intensity of each output light beam fluctuates with the number of the frequency components included in the electric signal. Such fluctuation of each output light beam brings about unevenness of printing and inevitably deteriorates the quality of printing.
Another conventional acoustooptic modulation system comprises a beam splitter in combination with a plurality of acoustooptic modulation elements. With this system, the beam splitter splits the incident light beam into a plurality of split light beams so as to supply the acoustooptic modulation elements with the split light beams, respectively. Accordingly, each of the acoustooptic modulation elements individually modulates each split beam by an acoustic wave resulting from an electric signal. As a result, a single modulated light beam is emitted from each acoustic modulation element in a direction dependent on each electric signal.
In order to produce a plurality of modulated light beams by the use of the above-mentioned system, a plurality of acoutooptic modulation elements should be arranged in parallel. The system therefore becomes bulky in structure. In addition, the acoustooptic modulation elements should individually be adjusted to the respective split light beams emitted from the beam splitter. Such individual adjustment is very troublesome.